DEVELOPMENT OF CuO/rGO NANOWIRE ELECTRODES FOR HYBRID ELECTROCHEMICAL SUPERCAPACITOR

Abstract

The development of high-performance and cost-effective electrode materials is crucial in advancing supercapacitor technology. For supercapacitors, nanostructured Cu oxides are promising materials due to their high theoretical capacitance, low cost, and non-toxicity. One major drawback to the practical applications of CuO lies in the poor electrical conductivity and cyclic stability of the material, despite its theoretically high specific capacitance. Here in, the CuO nanowire composite electrode coated with reduced graphene oxide (rGO) was prepared via a simple and scalable three-step method by anodization of a copper coated titanium substrate to grow copper hydroxide (Cu(OH)2) nanowires, dip coating with a graphene oxide (GO) dispersion, and thermal treatment of the electrode at 400 oC in a single step. The annealing converted Cu(OH)2 to CuO, and GO to rGO. X-ray diffraction (XRD) analysis confirmed the successful formation of phase-pure CuO, with prominent peaks observed. The SEM analysis confirmed the formation of a uniform CuO nanowire structure on Ti substrate. The electrochemical study revealed a synergistic charge storage mechanism, combining the electrical double layer capacitance of rGO with pseudocapacitance from CuO redox reactions. At a scan rate of 5 mVs-1 in CV, the rGO/CuO composite electrode gave the highest specific capacitance of 78.45 Fg-1 and current density of 0.25 Ag- 1 in Galvanostatic Charge Discharge (GCD); the composite electrode exhibited a maximum specific capacitance of 83 Fg-1. In addition, the electrode also showed excellent cyclic stability, after 1000 charge–discharge cycles at 5 Ag-1 current density, it retained more than 95% of its original capacitance. The observed enhancement in performance is due to high conductive pathways and the large surface area of the rGO network. In contrast, the CuO nanowires can deliver a significant amount of pseudocapacitance. The results suggest that the rGO/CuO composite prepared by this low-cost and effective method can be successfully implemented as an electrode material for the fabrication of high-performance hybrid supercapacitors.